public int DamerauLevenshteinDistance()

in languagetool-core/src/main/java/org/languagetool/rules/spelling/symspell/implementation/EditDistance.java [65:155]
76 lines of code
36 McCabe index (conditional complexity)

    public int DamerauLevenshteinDistance(String string2, int maxDistance) {
        if (baseString == null) return string2 == null ? 0 : string2.length(); //string2 ?? "").Length;
        if (string2 == null || string2.isEmpty()) return baseString.length();
        if(maxDistance == 0) return baseString.equals(string2) ? 0 : -1;

        // if strings of different lengths, ensure shorter string is in string1. This can result in a little
        // faster speed by spending more time spinning just the inner loop during the main processing.
        String string1;
        if (baseString.length() > string2.length()) {
            string1 = string2;
            string2 = baseString;
        } else {
            string1 = baseString;
        }
        int sLen = string1.length(); // this is also the minimum length of the two strings
        int tLen = string2.length();

        // suffix common to both strings can be ignored
        while ((sLen > 0) && (string1.charAt(sLen - 1) == string2.charAt(tLen - 1))) { sLen--; tLen--; }

        int start = 0;
        if ((string1.charAt(0) == string2.charAt(0)) || (sLen == 0)) { // if there'string1 a shared prefix, or all string1 matches string2'string1 suffix
            // prefix common to both strings can be ignored
            while ((start < sLen) && (string1.charAt(start) == string2.charAt(start))) start++;
            sLen -= start; // length of the part excluding common prefix and suffix
            tLen -= start;

            // if all of shorter string matches prefix and/or suffix of longer string, then
            // edit distance is just the delete of additional characters present in longer string
            if (sLen == 0) return tLen;

            string2 = string2.substring(start, start + tLen); // faster than string2[start+j] in inner loop below
        }
        int lenDiff = tLen - sLen;
        if ((maxDistance < 0) || (maxDistance > tLen)) {
            maxDistance = tLen;
        } else if (lenDiff > maxDistance) return -1;

        if (tLen > v0.length)
        {
            v0 = new int[tLen];
            v2 = new int[tLen];
        } else {
            for(int i = 0; i < tLen; i++) v2[i] = 0;    // Substituting Array.clear(v2, 0, tLen)
        }
        int j;
        for (j = 0; j < maxDistance; j++) v0[j] = j + 1;
        for (; j < tLen; j++) v0[j] = maxDistance + 1;

        int jStartOffset = maxDistance - (tLen - sLen);
        boolean haveMax = maxDistance < tLen;
        int jStart = 0;
        int jEnd = maxDistance;
        char sChar = string1.charAt(0);
        int current = 0;
        for (int i = 0; i < sLen; i++) {
            char prevsChar = sChar;
            sChar = string1.charAt(start+i);
            char tChar = string2.charAt(0);
            int left = i;
            current = left + 1;
            int nextTransCost = 0;
            // no need to look beyond window of lower right diagonal - maxDistance cells (lower right diag is i - lenDiff)
            // and the upper left diagonal + maxDistance cells (upper left is i)
            jStart += (i > jStartOffset) ? 1 : 0;
            jEnd += (jEnd < tLen) ? 1 : 0;
            for (j = jStart; j < jEnd; j++) {
                int above = current;
                int thisTransCost = nextTransCost;
                nextTransCost = v2[j];
                v2[j] = current = left; // cost of diagonal (substitution)
                left = v0[j];    // left now equals current cost (which will be diagonal at next iteration)
                char prevtChar = tChar;
                tChar = string2.charAt(j);
                if (sChar != tChar) {
                    if (left < current) current = left;   // insertion
                    if (above < current) current = above; // deletion
                    current++;
                    if ((i != 0) && (j != 0)
                            && (sChar == prevtChar)
                            && (prevsChar == tChar)) {
                        thisTransCost++;
                        if (thisTransCost < current) current = thisTransCost; // transposition
                    }
                }
                v0[j] = current;
            }
            if (haveMax && (v0[i + lenDiff] > maxDistance)) return -1;
        }
        return (current <= maxDistance) ? current : -1;
    }